Great Rift Valley

The Great African grave breach (English Great Rift Valley or East African Rift System (EARS ) ) is a rift zone, extending from East Africa to southwest Asia and originated by the cleavage of the Arabian plate from the African plate during the last 35 million years. It is believed that a newly emerging plate separated from the African plate along the grave breach, for which the term is used Somaliaplatte.

Researched and identified in its geological significance of the grave breach was first by the Scotsman John Walter Gregory, after which he is sometimes called Gregory Rift.

Expansion and development

The Great African grave breach is from its northern end Syria to its southern end in Mozambique around 6000 kilometers long. The width of the valley varies between 30 and 100 km, the depth of a few hundred to several thousand meters.

Orontes, the Jordan Rift Valley and Red Sea

The northernmost part of the Rift forms the course of the river Orontes ( Nahr al - Asi ) with the Ghab level (al- Ghab ) and the Bekaa (al- Biqa ), it follows the valley of the Jordan, the Jordan Rift Valley, where the flow through the Sea of ​​Galilee to the Dead Sea flows. Further south the Rift forms the Aravasenke and then the Gulf of Aqaba and the Red Sea.

At the southern end of the Red Sea was formed a branch. The Gulf of Aden is the eastern continuation. Before opening the Rift, the Arabian Peninsula was connected to the Horn of Africa; from here it becomes part of the mid-oceanic ridge of the Indian Ocean.

This line separates the Arabian plate from the African continental block.

East African rift

Southwest of the fault is now the continental Rift Valley ( East African Rift Valley), from its impressive dimensions, the entire Great Rift Valley originally got its name. In the Afar Triangle of ditch shares initially as Ethiopian ditch the geologically ancient Ethiopian highlands in the north-west highlands of Abyssinia and located the southeast location Somali Highlands.

Eastern and Western Rift ( Central African rift)

In East Africa, separates the valley in the Eastern Rift and the Western Rift, also called the Central African rift. Lake Victoria, the third largest lake in the world, is also considered part of the Rift Valley system although it actually lies between the two branches of the system.

The Eastern Rift loses something in the Kenyan highlands, in Kenya the valley is deepest to the north of Nairobi. Since there is no outlet to the sea here, the lakes tend to be shallow and have a high mineral content. By evaporation of the water, salt lakes and salt deposits form. Lake Magadi for example consists of soda ( sodium carbonate), Elmenteita Lake, Lake Baringo, Lake Bogoria and Lake Nakuru are all strongly alkaline, and Lake Naivasha needs fresh water supply to maintain its biological diversity.

The northern part of the western trench is also Albert Rift ( with Albert ) called, which continues in the Kivu Rift ( with Lake Kivu ) and in Tanganyika Rift ( with Lake Tanganyika ). It is accompanied by some of Africa's highest mountains and mountains, Virunga Volcanoes, Mitumba Mountains and Rwenzori Mountains National Park, and includes some of the deepest lakes in the world (including the up to 1,470 meters deep Lake Tanganyika ).

Southern Rift

The southern part, after uniting the two branches again, South Rift Valley and Lake Malawi Rift is named after Lake Malawi. It extends up into the Rift Valley Coast region called zone of the Indian Ocean in Mozambique, at the height of Madagascar, which is formed by the confluence of the Zambezi run.

The future

The Rift Valley is evolving: In a few million years the eastern Africa will probably split off from the rest of the continent and form a new separate land mass.

The tectonic activity that formed the Rift Valley, weakened the Earth's crust along its borders. The area is therefore volcanic and seismically active. It created the volcanoes of Mount Kenya massif, Mount Kilimanjaro, Karisimbi, Mount Nyiragongo, Mount Meru and Mount Elgon as well as the crater highlands in Tanzania. The Ol Doinyo Lengai volcano is still active and the only carbonatite volcano in the world.

Anthropological findings

The Rift Valley is a rich source of paleoanthropological discoveries, particularly in the Olduvai Gorge. The rapid erosion of the Highlanders filled the valley with sediments, which provide good conditions for the preservation fossils. So many fossils of early representatives of Hominini were (various Australopithecus and Homo species) have been found. Especially Richard and Meave Leakey made ​​many discoveries in this region.

Another well-known hominid point is the middle Awash region in the so-called Afar Triangle. From this area comes among others Lucy, an Australopithecus afarensis woman whose skeleton preserved in large parts was discovered there in 1974 by Donald Johanson.

The Rift Valley is considered according to the state of today's fossil record as the "cradle of mankind" ( Main place of humanization ), although some recent finds from South Africa and the Sahel region have the theory of evolution exclusively some perspective in this area.

Documentary

• Africa's Rift Valley. The big ditch. Documentary series in three parts á 43 min Part 1: In the Paradise of the animals. Part 2: From soda lakes and inland seas. Part 3: From Hellfire to the Holy Land. France, Austria, 2010 Director: Harald Pokieser, Paul Reddish, production: Arte, ORF, movie information of ARD.